1. Field of Invention
The present invention relates to a projector including an electro-optical device for forming an optical image according to image information, a projection lens for enlarging and projecting the image formed by the electro-optical device, a lens positioning mechanisms for adjusting the image projecting position, and an outer casing for covering the main bodies thereof.
2. Description of Related Art
Hitherto, a projector has been known which includes a light-source unit having a light source, an electro-optical device for forming an optical image according to image information by using a light beam emitted from the light source, a projection lens for enlarging and projecting the image formed by the electro-optical device, a lens positioning mechanism for adjusting the image projecting position, and an outer casing for housing these components.
Such projectors are widely used for multimedia presentations at conferences, academic meetings, exhibitions, and the like.
In this case, the brightness of a display screen is sometimes increased to improve visibility of the display screen in the projector.
In general, the brightness of the display screen is improved by stacking a plurality of projectors and superimposing images projected from the projectors. If the projecting positions of the images projected from the projectors are not completely aligned, displayed images are offset from one another.
For this reason, in conventional projectors, a projection lens is moved vertically by a lens positioning mechanism in order to adjust the projecting position of an image projected from the projection lens. The image offset can be prevented by adjusting the image projecting position in each of the projectors, and this improves brightness of the display screen.
Since heat-generating members, such as a light source, and a power-supply unit, are contained in the outer casing of the projector, the inside of the device needs to be efficiently cooled.
For that purpose, the outer casing for housing the components in the conventional projector is provided with a meshed air inlet having a size such that dirt and dust do not enter the inside of the device therethrough, and the inside of the device is reliably cooled by a larger amount of cooling air.
Although such a meshed air inlet can be simultaneously formed when the outer casing is formed by injection molding or the like, the size of each hole is substantially small, and clogging is sometimes caused by burrs or the like produced in molding. In such a case, it is necessary to perform unclogging, and to perform another operation of forming a complete air inlet through the outer casing. Since this takes a lot of labor, the operation of producing the outer casing, and the operation of manufacturing the projector are troublesome. Furthermore, a meshed air inlet is formed in the outer casing, and the outward appearance of the projector is impaired.
The present invention provides a projector in which the production of an outer casing is facilitated, cooling efficiency is maintained, and the outward appearance is preferable.
A projector of the present invention includes a light source, an electro-optical device for forming an optical image according to image information by using a light beam emitted from the light source, a projection lens for enlarging and projecting the image formed by the electro-optical device, a lens positioning mechanism for adjusting the image projecting position, and an outer casing for covering the bodies thereof. The projection lens is projected outside from an opening formed in the outer casing, and the clearance formed between the projection lens and the rim of the opening of the outer casing is filled with a dustproof ventilating member.
According to the present invention, since the projection lens projecting outside from the opening formed in the outer casing is moved, for example, vertically by the lens positioning mechanism in order to adjust the image projecting position, the opening of the outer casing is formed for the vertical movement of the projection lens.
In short, a sufficiently large clearance is formed between the rim of the opening of the outer casing and the projection lens so as to link the inside and the outside. By providing the dustproof ventilating member in this clearance, cooling air can be reliably drawn into the device via the ventilating member. Since this eliminates the necessity of forming a meshed air inlet in the outer casing, the production of the outer casing is facilitated, and the manufacturing operation of the projector is easily performed. Moreover, cooling efficiency is maintained well, and the outward appearance is made preferable.
In the above projector, it is preferable that the lens positioning mechanism includes a fixed member fixed to the side of the electro-optical device, and a movable member to which the projection lens is connected and which is slidably mounted on the fixed member, and that the space between the fixed member and the movable member be enclosed by an airtight member.
In this way, since the space between the fixed member and the movable member is sufficiently enclosed by providing the airtight member therein, there is no fear that light will leak from the sliding portion of the lens positioning mechanism.
In this case, when the surface of the airtight member is black, light that impinges on and is reflected by the light incident side of the projection lens can be absorbed by the airtight member. This makes it possible to sufficiently reduce reflectance inside the device.
When the airtight member is formed of a felt member, it is possible to improve the sliding ability of the movable member relative to the fixed member while ensuring sufficient air tightness between the fixed member and the movable member.
Furthermore, it is preferable that the lens positioning mechanism be operated by a rotary knob provided such that the rotary knob can be projected over and be retracted into the outer casing at will.
By doing this, when the lens positioning mechanism is operated, the rotary knob may be projected from the outer casing. Conversely, when the lens positioning mechanism is not operated, the rotary knob may be pushed into the device so as not to project from the outer casing.
Therefore, since it is satisfactory if the rotary knob is projected only in operating the lens positioning mechanism, there is no fear that the rotary knob will be broken against a desk or the like in carrying the projector, and handling is thereby facilitated.
In addition, when the rotary knob is depressed inside the device, the end portion of the rotary knob and the surface of the outer casing can be made nearly flush with each other. Therefore, the outward appearance of the outer casing is simplified, and the outward appearance of the projector is improved.